Re: [RFC PATCH 00/18] Add qemu-storage-daemon

[Kevin Wolf]

Am 06.11.2019 um 15:37 hat Max Reitz geschrieben:
> On 17.10.19 15:01, Kevin Wolf wrote:
> > This series adds a new tool 'qemu-storage-daemon', which can be used to
> > export and perform operations on block devices.
> 
> Looks good to me.
> 
> I remember a discussion at some KVM Forum a couple of years ago where
> someone (Berto?) was asking about adding QMP to qemu-nbd.  I found it a
> pragmatic solution, but I remember that Markus was against it, based on
> the fact that we wanted qemu -M none.

Yes, but it turned out that qemu -M none is a bit too heavyweight in
practice and fixing that would involve a lot of work. As I understand it
(mostly what I took from discussions on the list), even if someone were
interested in doing that and started now, it's the kind of thing that
would take multiple years.

As long as we keep the code simple and the interesting parts are just
reused and shared with the system emulator and other tools, it shouldn't
be hard to maintain.

> Well, but anyway.  Just as I didn’t have anything against adding QMP to
> qemu-nbd, I don’t have anything against adding a new application that
> kind of fulfills the same purpose.  And I think introducing a new
> application instead of reusing qemu-nbd that focuses on all-around QAPI
> compatibility (which qemu-nbd decidedly does not have) makes sense.

Yes, QAPI is one big reason for creating a new tool that doesn't need to
support the old qemu-nbd command line. Another is that we can add other
types of exports that are not NBD.

> The only thing I don’t like is the name, but that’s what <Tab> is for.
> :-)

I'm open for suggestions, but I thought 'qsd' was a bit too terse. :-)

(Actually, maybe we could even pick something that doesn't mention
storage or block? After all, it can do all kinds of QEMU backends in
theory. Not sure if there's any standalone use for them, but who
knows...)

Kevin

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